356 
MR. JOHNSTON ON THE CONSTITUTION OF THE RESINS. 
resins appear to be so related, yet that of assafoetida is not be considered as a hydrate 
of the resin of ammoniac. Thus the 
Carbon. 
First analysis gave 40 atoms. 
Second .... 40 atoms. 
Third .... 40 atoms. 
Fourth .... 40 atoms. 
Hydrogen. 
26*7 atoms. 
26*4 atoms. 
26*6 atoms. 
26*2 atoms. 
Oxygen. 
10T8 atoms. 
9*96 atoms. 
9*55 atoms. 
9*3 atoms. 
Now, allowing a similar error in the hydrogen in the four analyses, we see that the 
hydrogen and oxygen by no means diminish in the ratio in which they enter into the 
constitution of water. Taking No. 2 as the normal state of the resin, we find that in 
No. 4 the loss of hydrogen was 0'2 of an atom, while that of oxygen was 0*66, or three 
times as much as was necessary to form water with the hydrogen. In the volatile 
substance which escapes during the heating, therefore, the oxygen is to the hydrogen 
in atoms as 3 :1, while in the resin itself they are nearly as 2 : 5. We have seen that 
in ammoniac and opoponax resins, the volatile matter given off in heating to incipient 
decomposition, also contains more oxygen in proportion to the hydrogen than exists 
in the resin itself. 
III. As the resin, when heated gently over the lamp, and kept for a length of time 
in fusion, approached in composition to a formula containing nine of oxygen (see 
fourth analysis above), I heated a second quantity very gently under the same cir- 
cumstances, and kept it in fusion for six hours ; there was no frothing ; the resin 
nearly lost its smell, and became slightly darker in colour. It was more brittle, and 
the fragments showed still less tendency to cohere than before. 
6*42 grs. (6*407 grs. pure resin) gave C = 16*535, and H = 4*425 grs., or per cent., 
Carbon 71 '37 40 atoms. 
Hydrogen 7'66 26*3 atoms. 
Oxygen 20*97 9*05 atoms. 
100 
This result is in exact accordance with those of the other analyses, and with the 
remarks already made in regard to the comparative rapidity with which the- oxygen 
diminishes. For while the analysis of the resin in its normal state (No. 2) gave 
Carbon. Hydrogen. Oxygen. 
40 atoms. 26*4 atoms. 9*96 atoms, 
we have now obtained 40 atoms. 26*3 atoms. 9*05 atoms, 
so that by prolonged fusion at a temperature of about 250°, till it nearly loses its 
smell, the resin C 40 H 26 O 10 changes into C 40 H 26 0 9 . The changed resin is still easily 
and completely soluble in cold alcohol of 0*84. 
IV. We have seen that the alcoholic extract of the labdanumof commerce may be 
represented by C 40 H 33 0 8 , and that by boiling in water a resin C 40 H 33 0 7 # is obtained ; 
* See under labdanum resin, p. 345. 
